Joist for new sunroom, treated or not?

[czechsonofagun]

I am planning to build an enclosed porch/sunroom. The floor will be between 2' - 3' feet above the ground, the roof will overlap the footprint of course.

Should I use treated lumber for the floor joist? The joist will never get wet, but it will be - technically - outside. The joist will be attached to the house joist on one side, on the other side it will be supported by concrete footings. I will use treated lumber on top of the concrete, but the next layer, does it have to be treated too?

Thank you.

 

[oosik]

I built two small decks on my house 37 years ago. Neither deck has ANY treated lumber and they are weathered but still strong as ever. Neither is covered but there is unrestricted air flow around and below each one. I think the last time I put any type of weather proofing on either was twenty plus years ago.

Were I to redo either now - I would go the same route.

 

[czechsonofagun]

Thank you, I much more prefer to work with clean lumber if possible.

 

[prichard]

If dry and not on concrete no need for treated. Treated are not used for floor joists in a house even over dirt.

 

[kthompson]

If I read correctly the joist do not extend past the outside walls so only humidity is issue and not rain. I think if you need treated floor joist then you will need treated lumber for the sub floor also. If you have decent air floor under it should not have any issue.

 

[Bigkrank]

If you have termites that would be a reason for treated.

 

[prichard]

I read that wrong. I missed the porch part and only saw sunroom. Will the floor be enclosed by walls?

 

[czechsonofagun]

The porch in the original post refers to the fact that it will be elevated, unlike sunrooms built on the ground. Concrete footings/piers will hold treated lumber beams (nailed together 2x8s) about 2' to 3' above ground.

On those treated beams I will hang the joist using Simpson hangers, nail OSB subflooring on top of the joist and tiles for flooring. The underside of the floor will be exposed only to moisture with sufficient air flow. There will be no wall, only lattice.

 

[Snobdds]

You should be fine with non pressure treated wood...

 

[EddieWalker]

Air flow is the thing you have to keep in mind. Even with exposed decks, if there isn't enough air flow under the deck, the treated joists will become covered in mold, and the mold will eat away the lumber.

Your situation is similar to a pier and beam home, which never use treated joists.

If you don't need treated, it's smart not to use it. The way it's created now is horrible, and you never really know what it's going to do, or how much it's going to shrink, until it's all dried out.